JPMorgan Chase, facing criticism that it misled investors about a change to a risk model as trades backfired last year, told U.S. regulators that the bank wasn’t obligated to disclose the move until May.

Bloomberg reports that while there was an 'interim change' to the lender’s so-called value-at-risk model during the first three months of 2012, that adjustment had been reversed by the time the company filed its quarterly report in May, then-Chief Financial Officer Douglas Braunstein told the Securities and Exchange Commission in a December 3rd letter that was released Wednesday.

'As a result, the firm believes there was no model change within the meaning of' securities-disclosure laws, he wrote.

The alteration to the model in January 2012 has been blamed for exacerbating trading losses that exceeded $6.2bn last year. The bank disclosed the change and initial losses of about $2bn in a May 10 regulatory filing, almost a month after reporting first-quarter results.